Buttons and menus are named exactly as the app shows them.
Steps
Draw with a pen or a finger
Sketches read pen pressure where the device reports it, and the eraser end of a pen erases.
Get clean shapes
Rough shapes become clean ones, so a quick box is a box.
Add shapes, text and images
Place shapes, text boxes and pictures, then move, resize and rotate them.
Connect them
Connectors stay attached when you move things, which turns a sketch into a diagram.